Electric circuit interrupter



7 March 8, 1938. o. MAYR I ELECTRIC CIRCUIT INTERRUPTER Filed March 6, 1957 lnv Ott entor' Q Magr', y 1 :1]

H S Attorney Patented Mar. 8, 1938 UNITED STATES PATENT OFFICE 2,110,672 ELECTRIC CIRCUIT INTERRUPTER Otto MayrIBerlin-Karlshorst, Germany, assignor to General Electric Company, a corporation of New York Application March 6, 1937, Serial No. 129,422

In Germany March 23, 1936 4' Claims. (c1. zoo-149) ample, wherein an arc-extinguishing gas is re 7 leased from the walls of the arc chamber under '10 influence of the arc heat, there is often'encountered difiiculty in interrupting both large and small currents with equal facility. Phat is, since the amount of extinguishing gas generated depends, among other things, on the intensity of the arc current, thesize of the arc chamber is generally a compromise between the optimum for low current and high current interruptions. If

the capacity of the arc chamber is selected so that an effective gas expulsion takes place at low currents for interrupting the arc, the pressure generated during the interruption of a high current are may be so great as to burst the chamber casing. Converselyyif the capacity of the arc chamber is increased so as to provide for the larger amount of gas generated during interruption of a high currentarc, the expulsion effect at low currents may be soweak that the arc is not interrupted. i

The principal object of myinvention is the provision of .an improved circuit interrupter of the aforesaid type which is efiicient and positive in operation throughout its entire rated range of interrupting capacity, and simple and durable in construction.

5 In accordance with my invention in a simple form thereof an arc-extinguishing chamber is provided with a wall portion which is movable in responseto predetermined pressure within the arc chamber for automatically regulating the 40 pressure of the arc-extinguishing gas during interruption of currents throughout the rated range of the interrupter. In a preferred arrangement the movable wall portion is formed as a piston normally biased by a spring or the equivalent thereof so as to define a minimum arc-chamber volume. Predetermined arc pressure generated within the chamber is effective to move the piston against the biasing force so as to enlarge the arc chamber and thereby reduce bursting pressures during interruption of high current arcs. In the normal position of the piston, the restricted volume of the .arc chamber is such that small or medium currents are effectively interrupted by the gas pressure generated. therein.

I .My invention will be more fully 'set forth in the following description referring to the accompanying drawing, and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

Referring to the drawing the single figure thereof is an elevational'view, partly in section, of an electric circuit interrupter of the gas-expulsion type embodying the present invention.

The circuit interrupter shown by way of example is an expulsion type switch in the open circuit position. The switch or circuit breaker comprises essentially an extinguishing tube I or an equivalent structure forming an, arc-interrupting chamber I centrally of the tube. The tube I, or the walls of the arc chamber, is composed of a gas-yielding material such as, for example, fiber or hard rubber so that an arc-interrupting gas is generated within the arc chamber when the chamber walls are subjected to the arc. The closed end of the arc chamber I is located adjacent the fixed contact structure 2, which is shown as of the segmental type, suitably mounted within a stationary terminal housing 3. The coacting movable contact comprises a rod 4 movable through the open or gas exhaust end of the arc chamber into engagement with the fixed contact 2. The tube I is suitably secured to the fixed housing 3 in any suitable manner, such as by screw-threaded engagement.

The closed end of the arc chamber I is de-- fined by a movable wall portion 5 which is operable within a chamber 6 in the terminal housing 3 and suitably biased by a spring I into engagement with the fixed contact structure 2. In this position the movable wall portion, which in the present instance is formed as a piston, defines an arc chamber of minimum volume for the interruption of light or medium currents. That is, during the interruption of small or medium currents the piston 5 remains in the position shown and the are drawn between the contacts 2 and 4 acts on the inner walls of the chamber I to release the arc-extinguishing gas. When the rod contact 4 leaves the lower exhaust end of the chamber a gas blast takes place which interrupts the are. i .1

When comparatively large currents are to be interrupted, the chamber 6 serves as a compression chamber and the gas pressure generated within the arc chamber I forces the piston 5 upwardly against the bias of spring I to enlarge the volume of the arc chamber, thereby reducing the bursting pressure. A vent 8 can also be provided in the compression chamber 6, and if desired, may be formed as an adjustable throttle opening. This-permits a certain degree of adjustment in regulating the pressures to be relieved in accordance with the circuit-interrupting requirements of the switch.

A further advantage of the movable chamber wall as arranged in accordance with the present invention is that the energy stored in the spring ll during the initial circuit opening movement is returned. in the form or an augmented gas blast when the movable switch rod l clears the exhaust end of the arc chamber l. The piston, therefore, in returning to its-original position serves to aid final interruption of the arc.

It should be understood that my invention is not limited to specific details of construction and arrangement thereof herein illustrated, and that changes and modifications may occur to one skilled in the'art without departing from the spirit of my invention;

What I claim as new and desire to secure by Letters Patent" of the United States, is:

1. An electric circuit interrupter of the gasexpulsion type comprising means for opening the circuit, insulating structure defining a chamber having an exhaust opening within which an arc is formed upon opening of the circuit, said chamber having wall portions composed of a material adapted to emit an arc-extinguishing gas when subjected to said are, means forming a pressure resisting movable wall portion of said chamber, said wall portion being movable in a direction to increase the volume of said chamber substantially independently of the exhaust therefrom in response to predetermined gas pressure generated within said chamber, and means coacting with said movable wall portion forming an expansion chamber, from which gas is returned to said are chamber by said wall portion during the latter part of the circuit-opening operation.

2. An electric circuit interrupter of the gasexpulsion type comprising relatively movable contact structure, an insulating cylinder forming an arc chamber co-operating with said contact structure, a .i piston-like member forming a confining wall portion of said are chamber normally biased so as to restrict the volume of said chamber, said chamber also having wall portions composed of a material adapted to emit an arcextinguishing gas when subjected to the arc, said member being movable in a direction to enlarge the aforesaid arc chamber in response to predetermined gas pressure generated within said arc chamber upon separation of said contact structure, and means forming an expansion chamber within which said piston-like member operates, said member being biased to return gas under pressure to said are chamber for aiding interruption during the latter part of the circuit-opening operation.

3. An electric circuit interrupter of the gasexpulsion type comprising a fixed and a movable rod contact, an insulating cylinder forming an arc chamber through which said rod contact is movable for coacting with the other contact, said chamber having walls composed of a material adapted to emit an arc-extinguishing gas when subjected to the arc formed upon separation of said contacts, said contacts arranged to separate at one end of said chamber, means forming an expansion chamber at said one end of said chamber, and a piston forming a confining wall portion of said are chamber operable in the aforesaid expansion chamber normally biased so as to restrict the volume of said chamber, said piston being movable into said expansion chamber to increase the volume of said arc chamber in response to predetermined gas pressure generated during separation or said contacts, and operable to return gas under pressure to said arc chamber for aiding interruption when the arc pressure has decreased a predetermined amount.

a. An electric circuit interrupter of the gasexpulsion type comprising a fixed contact and a coacting movable rod contact, aninsulating tube having a sleeve-like fit with respect to said rod contact through which said contact is operable to engage said fixed contact at one end of said tube, said tube forming an arc chamber having walls composed of a material adapted to emit an arc-extinguishing gas when subjected to the are formed upon separation of said contacts, means substantially closing the end of said tube adjacent said fixed contact, a piston member disposed within said closing means adjacent said end of said tube, said piston being normally biased so as to restrict the volume of said are chamber, said piston being movable in opposition to said bias to increase the volume of said arc chamber in response to predetermined gas pressure generated within said chamber.

OTTO MAYR. 

